306 M. M. Mercatr 
page 270, shows the refractive spherules in the macronucleus and 
in the groups of granules into which it fragments.) In higher 
Ciliata distinct vegetative and reproductive nuclei are present, but 
there are but few indications that the refractive spherules in the 
cytoplasm, are formed by the macronucleus. Each nucleus of Opalina 
is functionally comparably to both micronucleus and macronucleus 
of higher Ciéliata, and is in much more primitive condition. 
The formation of chromatin spheres in Opalina and their ex- 
trusion from the nucleus before copulation seems comparable to the 
formation of vegetative chromidia in Plasmodroma and is probably 
primitive. The degeneration of the macronucleus in higher Ciliata 
is probably somewhat comparable. 
The conditions of maturation in Opalina seem simpler than 
those in higher Ciliata. In the maturation of higher Czlzata the 
nuclear divisions unaccompanied by cell-division have generally been 
discussed from the standpoint of cytophysiology or of the mechanism 
of heredity.1) The conditions in Opalina seem to indicate that the 
degeneration of the nuclei in maturing Paramaectum and other 
higher Ciliata is secondary and is connected with the suppression of two 
divisions of the cell body. In Opalina there is no such suppression 
of divison of the cell body and there is no degeneration of nuclei 
or cells in connection with maturation. In the division of the 
macrogamete mother-cells in Opalina both daughter cells become 
functional gametes; similar relations obtain in the formation of 
Opalina’s microgametes. In Paramaecium three of the four nuclei 
(that is three of the four daughter cells) resulting from the matura- 
tion divisions in the similar gametes degenerate. In Metazoa sper- 
matogenesis follows the type found in Opalina, maturation producing 
four functional gametes, but in the maturation of the eggs of 
Metazoa usually one functional gamete and three degenerate gametes 
(polar bodies) arise. The fact that the polar bodies are capable of 
fertilization and development (cf. Francorre 1897) seems to show 
beyond doubt that the usual interpretation of the polar bodies as 
degenerate gametes is correct. 
Complete fusion of the gametes as in Opalina and the Vorticellas 
is doubtless more primitive than such temporary partial union, with 
exchange of parts of the nuclear material, as we see in Paramaecium. 
1) Bovert (1892b) is the only one, so far as I know, who has discussed the 
phenomena of maturation in Ciliata from the comparative morphological point of 
view and has recognised that the two maturation divisions here, as in the matura- 
tion of the eggs of Metazoa, give rise to rudimentary individuals. 
